Systems' latency - the time between user input and system response - slows down the human-computer interaction loop. Several studies revealed negative objective and subjective effects of high latency, typically treating latency as a constant delay. Because latency varies significantly in practice, recent work also assessed the effects of large and sudden latency changes. In practice, however, latency variations are small but frequent.
As the effects of such variations are unclear, we investigate how small latency variations (± 50 ms) affect users' performance and perceived task load for 2D target selection tasks with static and moving targets.
For static targets, we found that latency variation causes significantly higher completion times and less efficient trajectories, however with small effect sizes. In contrast, we found no significant effects on any performance measure for moving targets.
Our findings indicate that the effect of latency variation is generally very small and quickly disappears for non-trivial tasks.